Depends on the style of plastic. Most fishkeepers who own Male bettas with long fins tend to stay away from plants made of plastic cause they tend to have rough edges and more prone to damaging fins as they get snagged, etc.
I used to not think plastic plants were all bad, but I switched to silk and they make the tank look so amazing. I only bought 2 silk plants and with some modifications divide them up among 3 sections in the tank. I also modified the old plastic plants to make interesting decor that the bettas can't get to. Don't be afraid to modify, because then you'll have unique decor no one else has!
You can also do those little cute things they have in the stores, like castles or fake soccer balls or whatever. Some bettas like hiding places, so caves can work too. You just have to make sure there aren't any edges that the fish might catch on, as scootshoot said.
I do a combination of silk and plastic. I just make sure the plastic is soft not stiff. Also consider using a coffee mug or a ceramic pot for an inexpensive hidey hole. Not all of mine use it but lounge in the fake plants. I like them to have the option though. My king male, Sumo, likes his bridge.
You can actually get plastic plants that are more like rubber, I have them and love them, I've actually decided to completely convert to plastic plants in both my community and betta tank and they don't look all that fake either, which is a plus for me :D